1. Field of the Invention
The present invention generally relates to a vertical vibrator, and, more particularly, to a vertical vibrator, designed to achieve a stable vibration waveform by absorbing contact noise and impact caused by contact between a vibration part and an upper structure upon excessive upward vibration of the vibration part, to ensure convenient and appropriate positioning of magnetic fluid by use of the magnetic flux leaked from a yoke, and to have an extended life span by increasing coupling force between a magnet and the yoke.
2. Description of the Related Art
Communication instruments generally employ ring tones and vibration in order to notify call termination. Notification of the call termination using the vibration is generally performed in such a manner that driving force is generated by a small vibration motor, and is then transmitted to a casing of the instrument to vibrate the instrument.
The vibration motor, one of call termination-notifying means employed by current communication instruments, such as mobile phones, is a component which converts electric energy into mechanical energy by use of a principle of generating electromagnetic force, and is mounted on the mobile phone for the purpose of mute notification of call termination.
However, as a result of the rapid expansion of the mobile phone market together with the rapidly increasing diversity of mobile phone functions, there are requirements for miniaturization and high quality of components in the mobile phone, and under such circumstances, there is a need in the art to develop products employing a new structure capable of solving problems of conventional vibration motors while remarkably enhancing the quality of the conventional vibration motors.
FIG. 1 is a cross-sectional view of a conventional vibration motor. As shown in FIG. 1, the conventional flat-type or coin-type vibration motor comprises a stator 20, a rotor 10 rotatably equipped around a shaft 31, and a housing 30 for receiving the rotor 10 and the stator 20.
When power is applied from an external power supply to a pair of brushes 25 mounted on a lower substrate 21 of the stator 20, oppositely polarized electric currents are induced within the pair of brushes 25. At this time, since upper ends of the brushes 25 resiliently contact a commutator 15 provided on a lower surface of an upper substrate 11 of the rotor 10, power is supplied to a wound coil 12 provided in the rotor 10 through the commutator 15 contacting the brushes 25.
Then, the rotor 10 rotates in one direction around the shaft 31 by virtue of interaction between an electric field caused by electric current induced to the wound coil 12 and a magnetic field caused by a magnet 22 provided to the stator 20.
At this time, a contact between the brushes 25 and segments of the commutator 15 contacting the brushes 25 is continuously changed every cycle of rotation of the rotor 10, causing the polarities of the power source to be continuously changed. As a result, while continuously rotating, the rotor 10 having an eccentrically disposed weight 13 induces the vibration, which notifies the call termination.
In FIG. 1, reference numeral 14 indicates an insulating material which surrounds the wound coil 12 and the weight 13, reference numeral 32 indicates a bearing member, and reference numeral 30 indicates a bracket closing an open lower portion of the housing 30.
The vibration motor 1 generates mechanical vibration by rotating the rotor 10 having the eccentrically disposed weight when power is supplied thereto, and rotational force of the rotor 10 is generated through operation of the commutator or brush structure as current is supplied to the wound coil of the rotor 10 after being rectified through the contact between the brushes 25 and the commutator 15.
However, when driving the motor having such a structure, the brushes 25 pass through a minute gap between segments of the commutator 15, generating mechanical friction, electrical sparks and abrasion therein, whereby foreign substances, such as black powders, are produced, and reduce the life span of the motor.
Accordingly, in order to overcome the disadvantages of the conventional commutator or brush-type vibration motor, a multi-functional actuator has been developed which induces sound and vertical vibration by use of resonance frequency of a vibrator.
FIG. 2 is a cross-sectional view of a conventional multi-functional actuator. As shown in FIG. 2, an actuator 2 comprises a body casing 40 having a space defined therein, a trembling plate 50 mounted to an upper portion of the body casing 40 and having a sound coil 52 mounted on a lower surface of the trembling plate 50 for generating sound to indicate call termination, a magnet 60 vertically magnetized to form a magnetic circuit with an upper plate 62 mounted on an upper surface of the magnet 60, the upper plate 62, a vibrating body constituted by a weight 65 and a yoke 64 for mounting the magnet 60, a plate spring 66 for resiliently supporting the vibrating body within the body casing 40, and a vibration coil 42 provided to a position directly below the vibrating body for generating vibration.
In FIG. 2, reference numeral 43 indicates an upper case for covering an upper portion of the body casing 40, and reference numeral 44 indicates a bracket for receiving the vibration coil 42.
The actuator 2 is adapted to selectively generate sound and vibration by supplying power from the external power supply to the sound coil 52 and the vibration coil 42 through a lead line (not shown). In the actuator 2, if power is supplied to the sound coil 52, the trembling plate 50 minutely trembles by virtue of an interaction between the magnetic field generated by a magnetic circuit constituted by the magnet 60, the upper plate 62 and the yoke 64, and the electric field generated by the sound coil 52, thereby producing sound.
Additionally, if power is supplied to the vibration coil 42, the vibrating body vertically vibrates by virtue of an interaction between magnetic field generated from the magnetic circuit constituted by the magnet 60, the upper plate 62 and the yoke 64, and electric field generated from the vibration coil 52, in which the vibration body comprising the magnet 60, the upper plate 62, the yoke 64 and the weight 65 is suspended in the body casing 40 via the plate spring 66.
At this time, the vibrating body is subjected to variation in magnitude of movement thereof according to intensity and frequency of the signal for generating the vibration, and if a vertical amplitude of the vibrating body is above a predetermined value, the vibrating body comes into contact with the sound coil 52 provided as an upper structure or the vibration coil 42 provided as a lower structure, thereby generating contact noise. Accordingly, as shown in FIG. 2, the yoke 64 is provided at a lower surface with a magnetic fluid 70 acting as a damper for absorbing impact upon contact between the vibrating body and the lower structure.
However, the conventional actuator 2 described above has a number of limitations due to the number of components and complicated construction thereof. Namely, miniaturization and simplification of the conventional actuator 2 are limited and manufacture thereof is costly.
Accordingly, in order to overcome the problems of the conventional actuator 2, a vertical vibrator 3 has been developed, which generates vertical vibration, and has a small number of components as well as a simple construction.
FIG. 3 is a cross-sectional view of a conventional vertical vibrator. As shown in FIG. 3, the conventional vertical vibrator 3 comprises a casing 81 having a space of a predetermined size defined therein, a magnet 82 vertically magnetized and having a lower plate 83 mounted on a lower surface of the magnet 60, a yoke 84 to which the magnet 82 is mounted to form a magnetic circuit, a spring member 86 mounted between the casing 81 and the yoke 84 to vertically vibrate a vibrating body comprising a weight 85 mounted to the yoke 84, and a vibration coil 87 provided on an upper surface of a bracket 88 for closing a lower portion of the casing 81.
Operation of the vertical vibrator 3 constructed as described above is performed in the following fashion. When power is supplied to the vibration coil 87, the vibrating body vertically vibrates by virtue of interaction between a magnetic field generated from a magnetic circuit constituted by the magnet 82, the lower plate 83, and the yoke 84 and an electric field generated from the vibration coil 87, in which the vibration body comprising the magnet 82, the lower plate 83, the yoke 84 and the weight 85 is suspended within the casing 81 via the spring member 86.
However, if vertical displacement of the vibrating body meets or exceeds a predetermined maximum value during operation of the conventional vertical vibrator 3, the vibrating body comprising the spring member 86 generates contact noise through direct contact with the casing provided as an upper structure. This contact noise is the main source of noise associated with operation of the vertical vibrator.
Moreover, if bonding force between the yoke 84 and the magnet 82 is low, as determined by drop testing, the magnet 82 can be easily separated from the yoke 84, thereby increasing the frequency of defective products.